The present invention relates generally to alloys formed for structural use at high temperatures. More particularly, it relates to an iron-base structural alloy having a novel ruthenium content and adapted to use at high temperatures. It is known that jet engines operate more efficiently at higher temperatures than at lower temperatures. Increase in the operating temperature of an engine can give the engine itself higher performance characteristics. One of the great difficulties in achieving higher operating temperatures in jet engines and in other gas turbines is the lack of materials for the building of engines which can tolerate such high temperatures.
Engines are presently built with nickel-base alloys and more particular nickel-based superalloys which display high strength at high temperatures. However, for more advanced engines the temperature of the materials themselves would be above the temperature at which the conventional nickel-base superalloys will be molten.
Again, one of the basic problems of increasing the operating temperature of engines is that of finding materials which have suitable combination of properties for use at the higher temperatures. The temperatures of structural components in the hottest sections of such engines are envisioned to range from about 1250.degree. C. (2300.degree. F.) to temperatures which are reached when stoichiometric ratios of gas and air are burned. As noted above, such temperatures are above the melting point of presently used nickel-base superalloys. Because of the distinct advantages in the operating at such elevated temperatures, efforts have been made to find alloys from which structural components for use at such temperatures can be formed. If such engines can be built, there is a reward of a greater thrust to weight ratio possible as an improvement over present designs.
Numerous metallic systems have been investigated to determine the hottest temperature at which components of higher temperature jet engines can be employed as structural members. It is known that efforts have been expended to develop ceramic systems for use in the hottest components of such engines. The ceramic systems have the advantage of low density thus increasing the thrust to weight ratio, but they suffer from a lack of, or a lower order of, ductility. The metallic systems which have been studied for such applications include metal matrix composites as well as low density intermediate phases and intermetallic compounds. However, none of these compositions have been found to provide the combination of properties which are needed for structural use in the very high temperature engines.